War of Bohemian Succession (1125–1126)

Background

Since Duke Bretislaus I introduced agnatic seniority in the 11th century, succession in Bohemia often led to warfare among Přemyslid claimants. Formal recognition by the Holy Roman Emperor was sought, but actual accession required support from the Bohemian nobility. Duke Vladislaus I, ruling from 1109, faced challenges from his brother Bořivoj II, who had been enfeoffed by Emperor Henry IV in 1101. Otto appealed to agnatic seniority and gained support from Vladislaus' widow Richeza of Berg and King Lothair III.

Battle of Chlumec

In November 1125, King Lothair met Bavarian nobles in Regensburg, where they planned a campaign into Bohemia favoring Otto the Black, who had offered a considerable sum of money. The Bohemian nobles received an ultimatum to expel Soběslav or face a punitive expedition. Duke Soběslav I prepared for war, rallying the Bohemian aristocracy by invoking Saint Adalbert of Prague and Duke Wenceslas. During the winter of 1125–26, he built defensive works and encampments along the Kulmer Steig route.

On February 18, as the thaw set in, Lothair crossed the Bohemian border at the Nakléřov Pass with his army and met Soběslav's troops near Chlumec or the Lotarův vrch near Jílové. A vanguard of about 200 heavy armored knights under Otto the Black was attacked in a narrow valley, while the main army under Lothair became trapped. The battle ended in a crushing Imperial defeat; Otto fell, and Lothair was captured along with Margrave Albert the Bear and Landgrave Louis I of Thuringia. Soběslav released his captives on the condition of his investiture.

Did You Know?

• To commemorate his victory, Soběslav had a rotunda built on top of Říp Mountain, consecrated by Bishop Jindřich Zdík.
• The rotunda is one of the oldest Czech national monuments.